Long wearing papermakers&#39; dryer-felt



April 21, 1959 T. HINDLE ETAL LONG WEARING PPERMAKERS DRYER-FELT FiledJuly 26, 1955 2 Sheets-Sheet 1 April 21, 1959 T HlNDLE ET AL 2,882,933

LONG WEARING PAPERMAKERS DRYER-FELT Filed July 26, 1955 2 Sheets-Sheet 2United States Patent() LONG WEARIN G PAPERMAKERS DRYER-FELT ThomasHindle, Blackburn, England, and Edward H. Hall, Fitchburg, Mass.

Application July Z6, 1955, Serial No. 524,410

13 Claims. (Cl. 139-426) This invention relates to papermakersdryerfelts. In papermaking, dryer-felts in the form of endless wovenbands are used to carry the sheet or web of paper in close contact withthe drying cylinders of the papermachine. Although such dryer-felts,being composed of cotton or other cellulosic material or a mixturelthereof with asbestos, are not subjected to any form of milling, andare therefore not felts in the technical sense of the term, they have,by common usage, become universally known as dryer-felts.

Such dryer-felts are subject to severe mechanical stresses due toreverse bending around the drying cylinders :and intermediate feltrolls, which latter are usually driven by the felts. They are alsosubject to abrasion and to heat combined with the action of certainacids which are absorbed by the dryer-felt in a cumulative manner.

Dryer-felts are commonly woven from cotton or combinations of cottonland asbestos yarns. Cotton has excellent drying properties, but has thedisadvantage that its strength is lost under the combined action ofacids and heat. Asbestos has pronounced resistance to heat, and in thisrespect is preferable to cotton, but since the asbestos fibre is veryshort, yarns produced from pure asbestos have very little tensilestrengh. For that reason, asbestos yarns usually contain a certainproportion of cotton or lrayon fibre mixed with the asbestos libre, andusually have a core of cotton or rayon yarn to provide additionalstrength.

Because of their great tensile strength and superior resistance toabrasive action and to destructive chemical action, yarns of certainsynthetic fibres have been suggested as a substitute for cotton or theother natural libres commonly employed in the manufacture of dryerfelts,and experiment has shown that -a felt woven from such yarns alone has auseful life as much as four times that of the customary cotton felt.However, the high cost of synthetic yarns spun from staple lengthsynthetic fibres has precluded their use for thisvpurpose, except incertain specific locations, for example, in the margins of thedryer-felt. On the other hand, pure filament yarns, although cheaperthan the spun yarns, have certain inherent characteristics which make itimpractical to use them alone in the manufacture of a dryer-felt.

The present invention has for its object the production of acommercially practical dryer-felt having a substantially longer lifethan that of the customary cotton or asbestos felt.

As the result of extended experiment and practical test under paper millconditions, we have discovered that by a proper combination of syntheticlila-ment yarn with cotton or with cotton and asbestos, it is possibleto obtain many of the advantages of the synthetic material, as comparedwith pure cotton, in an acceptable felt whose cost is low enough to makeit commercially practical. More specically, we have discovered that ifconventional smooth-surfaced lament nylon, for example, be cornbinedwith cotton, so that the nylon lconstitutes from 6% to 14% of the wholeby weight,.to form a yarn ICC wherein the cotton constitutes a coreabout which the nylon is wound to form an open helix, and this compositestrand be employed for both Warp and ller in weaving a dryer-feltaccording to customary procedure, the resultant felt has a useful lifewhich is approximately 50% greater than that of a felt of similar weaveconsisting of cotton yarn alone. However, these experiments show that ifthe synthetic material be increased beyond 14% of the whole, by weight,the corresponding added length of useful life of the felt is sorelatively slight as to more than be counterbalanced by thecorresponding increased cost of the material employed.

Other and further objects and advantages of the invention will bepointed out in the following more detailed description and by referenceto the accompanying drawings, wherein Fig. 1 is a fragmentary plan viewillustrating diagrammatically a piece of papermakers dryer-felt made inaccordance with the present invention;

Fig. 2 is a fragmentary View to a very large scale, diagrammaticallyillustrative of the construction of one of the composite warp or weftstrands employed in weaving the fabric of Fig. 1;

Fig. 3 is a diagrammatic transverse section on the line 3--3 of Fig. 2but to larger scale;

Fig. 4 is a large-scale diagrammatic view showing a piece of one of thecomposite warp or weft strands untwisted until the core yarns areparalell, and showing the synthetic lament yarn as it then appears; and

Fig. 5 is a diagram graphically illustrative of the beneficial effectsof the present invention as respects increased useful life of thedryer-felt.

Referring to the drawings, Fig. l represents a piece of dryer-feltembodying the present invention and comprising the warps W and wefts F,it being understood that the warps and wefts are interwoven to provide amulti-ply fabric in accordance with any customary weaving procedure inthe manufacture of dryer-felts. It is also to be understood that thewarps and wefts are alike in respect to the ratio of lamentous syntheticand cotton contained therein, although it is immaterial whether thetwist of the warps be of the same or of a different hand from that ofthe wefts. As usual in the manufacture of dryer-felts, each warp or weftcomprises a plurality of cotton yarns plied together, but in accordancewith the present invention one or two yarns of filamentous synthetic,for example, nylon, is or are wound .about the plied cotton yarns. Theterm filamentous synthetic as herein employed is intended to designate astrand consisting of conventional smoothsurfaced filaments of a man-madefibre produced for example, by extrusion, and is to be distinguishedfrom a strand made by chopping up or otherwise dividing extruded lamentsand thereafter forming the short sections into yarns by spinning. Amongthe synthetics which have been found to provide the desiredcharacteristics in the dryer-felt in accordance with the presentinvention are nylon, which is a polyamide resin made by thepolymerization of a hexamethylenediamine salt of adipic acid; Orlon,which is made principally from polyacrylonitrile and which is made andsold commeroially by E. I. du Pont de Nemours & Company, this materialhaving high resistance to acids and to degradation by sunlight; andDaeron, which is made by the condensation of dimethyl terephthalate andethylene glycol, and which is made and sold commercially by E. I. duPont de Nemours & Company; these several synthetics being within thatgroup of synthetifcs commonly referred to as of the high tenacity type.

In accordance with the present invention, the number and size yof thecotton yarns which are plied together in making the core of the warp orweft strand may be.

Patented Apr. 2l, 1959 varied as desired, according t the type of cottonemployed, or with respect to the particular requirements of the mill inwhich the felt is to be used, but in accordance with the presentinvention, the winding of filamentous 'synthetic should constitute from6% to 14% and preferably of the total weight of the felt which is to bewoven.

As shown graphically in Fig. 5, wherein the ordinates represent usefullife of the felt and the abscissa represent the ratio of synthetic tocotton, the average normal life of a plain cotton felt of customaryconstruction is indicated by the numeral 1. lf, in manufacturing a felt,a filamentous synthetic, for example nylon yarn be substituted for someof the usual cotton yarns in making the warps and wefts, the useful lifeof the felt is thereby prolonged, but for` some unknown reason theincrease in useful life resultant from increase in the percentage ofsynthetic is not according to a straight line ratio, such as might beexpected and which is indicated by the dotted line 1-4, but as thesynthetic 4is substituted for cotton, the useful life of the resultantfelt rises very sharply and at a much higher rate than the rate ofincrease of the synthetic-cotton ratio, as shown by the curved portionof the solid line 1--4. This abnormal increase in useful life is suchthat by a substitution of 10% of filamentous synthetic for an equalamount of cotton, the useful life of the felt is increased byapproximately 50% or more. However, after the synthetic reaches 14%, bylweight, of the whole, further increase in the percentage of syntheticdoes not show any similar abnormal increase in the useful life of thefelt, but beyond 14% of synthetic, increase in useful life isapproximately in a straight line ratio to the increase in percentage ofsynthetic, as indicated by the solidline X-4.

The cost of filamentous synthetic is so much greater than the cost ofcotton that increase in the amount of synthetic beyond 14% issubstantially balanced by the increased cost of the felt, so that forpractical purposes 14% of synthetic in a felt, wherein the balance iscotton, represents the upper useful substitution of synthetic forcotton, and as will be seen by inspection of Fig. 5, this 14% syntheticrepresents an increase of useful life of the felt of approximately 60%.However, the abnormal rate of increase is most manifest up to 10%synthetic, and it is at present considered that 10% synthetic representsthe best practice as respects prolonged life as balanced againstincreased cost.

In the drawings (Figs. 2, 3, and 4) a composite strand such as lis usedin the practice of the present invention, and which may be a warp orweft strand, is illustrated, the views being diagrammatic.

In preparing the composite warp strands W or the composite weft strandsF (Fig. l) according to the present invention, cotton yarns C (Figs. 2,3 and 4) of the selected size and in the desired number are twistedtogether to form a plied strand. While so twisting the cotton yarnsktogether, one or more filamentous synthetic nylon strands are deliveredto the twisting point at substantially zero tension, while concurrentlythe cotton yarns are delivered at a positive tension, the differencebetween these tensions being such that in the completed composite strandthe synthetic yarn tends to lie on the surface, thus `forming in the onetwisting operation an open-coiled helix or spiral winding exposed at thesurface of the bundle of plied cotton yarns which form the core of thestrand. Obviously the synthetic yarn could be wrapped about the cottoncore as a separate operation if desired. Because the synthetic yarn hasa much higher tensile strength than the cotton yarn, offers greaterresistance to abrasion, is less easily damaged by chemical action, andis exposed at the surface of the bundle of cotton yarns forming thecore, it provides added strength to resist tension and flexing, andprotects the cotton core yarns from the eiects of abrasion and chemicalaction, and thus, although these windings'of synthetic yarn form but asmall percentage of the entire felt, nevertheless the synthetic yarnapplied as above described adds very substantially to the useful life ofthe felt, as above pointed out and illustrated in Fig. 5 of thedrawings.

Not only does the substitution of a relatively small amount of syntheticyarn for a similar amount of cotton add materially to the useful life ofa felt which is otherwise of pure cotton, but a generally similarincrease in useful life may begiven to a so-called asbestos felt inaccordance with the present invention by the addition thereto of a smallpercentage of filamentous synthetic yarn. Usually an asbestos felt is ofmulti-ply construction comprising a backing ply or plies of pure cotton,yarn, and a facing ply or plies of asbestos yarn, the latter usuallycontaining a certain proportion of cotton or rayon fibres mixed with theasbestos fibre before the spinning process., and usually having a coreof cotton or rayon yarn to provide additional strength. In accordancewith the present invention, the warps and wefts which form the backingof the asbestos felt may be made in the manner above described by plyingcotton yarns and winding a filamentous synthetic strand about the bundleconstituted by the plied cotton yarns,.the synthetic strand and cottonbeing in proportions such that the percentage of synthetic falls withinthe range fromy 6% to 14% by weight, but preferably being 10% synthetic.

In making the composite yarn for warp or weft as above noted, and merelyby way of example 10s/7 cotton yarns may be plied together and woundwith one or more filamentous synthetic yarns, the latter being of suchdenier that the completed yarn will contain the synthetic in thepercentage, by weight, above described. Merely by way of a furtherexample, 7s/ 5 cotton yarn may likewise be plied together and wound withone or more synthetic filamentous yarns of such denier as to produce theabove desired percentage. In forming the composite strand, any desiredtwist may be employed, for instance, the composite strand may have seventurns per inch, either in the Z or S direction, it being understood,however, that these specific examples are merely by way of illustrationand not in any sense designed to indicate limitations upon theinvention.

It is further to be understood that any and all modifications which fallwithin the terms of the appended claims are to be considered as. withinthe scope of the invention.

We claim:

1. A- papermakers dryer felt wherein, throughout its entire width, bothwarps and wefts comprise cores consisting of plied cotton yarns andexposed helical windings of abrasion resistant filamentous syntheticmaterial which ride on the cotton cores, the synthetic materialconstitutingfrom 6% to 14% of the whole felt by weight.

2. A papermakers dryer felt comprising cotton and from 6% to 14% byweight of a filamentous synthetic material which is abrasion resistantand of high exural endurance, each of the warps land each of the weftshaving a core consisting of plied cotton yarns and an external windingcomprising a plurality of spaced helices of the filamentous syntheticmaterial which ride on the bundles of cotton yarns.

3. A woven papermakers dryer felt which has a useful life approximating50% greater than that of a similarly constructed felt consisting ofcotton alone, said felt comprising cotton and approximately 10% byweight of a filamentous synthetic material which is strong and abrasionresistant, the felt consisting of interwoven warps and wefts, each warpand each weft comprising a core consisting of'plied cotton yarns, thefilamentous synthetic material being so associated with the cotton coresas to form an exposed helical winding which embraces and rides on thelatter.

and each of the wefts comprising a core of cotton and an externalopen-coiled helical winding of filamentous nylon, the nylon constitutingfrom 6% to 14% by weight of the felt.

5. A paperrnakers dryer felt wherein warp and weft strands areinterwoven in customary manner to form a multi-ply fabric, certain ofthe constituent strands which appear at the face of the fabriccomprising asbestos bre, and others of the constituent strands, whichconstitute the back of the fabric, each comprising plied cotton yarnsand a yarn of a strong, abrasion resistant filamentous synthetic, thecotton yarns forming the core of the strand and the filamentoussynthetic yarn forming an openspired helical winding exposed at thesurface of the core, and riding on the latter, the filamentous syntheticmaterial so employed constituting approximately 10% by weight of thefelt.

6. A papermakers dryer felt, according to claim 1, wherein thefilamentous synthetic material is of the high tenacity type.

7. A papermakers dryer felt, according to claim 1, wherein the syntheticmaterial is filamentous nylon.

8. A papermakers dryer felt, according to claim 1, wherein the syntheticmaterial is filamentous Daeron.

9. A papermakers dryer felt, according to claim l, wherein the syntheticmaterial is filamentous Orlon.

10. A multi-ply papermakers dryer felt wherein warp strands and weftstrands are interwoven to form a multiply fabric, certain of theconstituent strands, which appear in the face ply of the fabric,comprising asbestos bers, and others of the constituent strands whichare in the rear ply of the fabric each comprising plied cotton yarns andfilamentous nylon, the cotton yarns forming the core of each suchstrand, and the nylon yarn forming an open-spired helical windingexposed at the outer surface of the core and riding on the latter, thenylon so employed constituting approximately 10% by weight of thefabric.

11. A papermakers dryer felt which comprises warp and weft strands whichare so interwoven as to form a textile fabric structurally suitable foruse as a dryer felt, each of the strands so employed comprising a coreconsisting of a plurality of cotton yarns twisted together, said corebeing embraced by at least one winding of lamentous synthetic yarn whichlies on the surface of the cotton core in the form of an open-coiledhelix, the total amount of synthetic filamentous material comprised inthe felt constituting from 6% to 14% by weight of the felt.

12. A papermakers dryer felt consisting of interwoven warp and weftstrands of non-felting fibrous material, certain at least of theconstituent strands each having a plied core whose constituent yarnsconsist of bre of natural origin, the core being embraced by at leastone protective winding of lamentous smooth-surfaced synthetic yarn ofthe high tenacity type disposed to form an open-coiled helix coaxialwith the core, said helix riding upon the core with its turns exposed atthe outside of the core, the total amount of lamentous synthetic soemployed in the felt constituting from 6% to 14% of the total weight ofthe felt.

13. A papermakers dryer felt consisting of interwoven warp and weftstrands wherein each of the warp and weft strands has a core consistingsolely of cotton yarn, said core being embraced by a winding offilamentous, smooth-surfaced yarn of a synthetic of the high tenacitytype which forms an open-coiled helix coaxial with and riding upon thecore, the synthetic yarn constituting from 6% to 14% of the total weightof the felt.

References Cited in the le of this patent UNITED STATES PATENTS2,098,993 Barrell Nov. 16, 1937 2,115,658 Whittier Apr. 26, 19382,168,928 Barrell Aug. 8, 1939 2,423,828 Chagnon July 15, 1947 2,449,595Ellis Sept. 21, 1948 2,506,667 Hall May 9, 1950 2,540,874 Geddings Feb.6, 1951 2,552,210 Parker May 8, 1951 2,575,753 Foster Nov. 20, 19'51FOREIGN PATENTS 472,893 Canada Apr. 17, 1951 710.078 Great Britain June94 1954

1. A PAPERMAKER'' DRYER FELT WHEREIN, THROUGHOUT ITS ENTIRE WIDTH, BOTHWRAPS AND WEFTS COMPRISE CORES CONSISTING OF PLIED COTTON YARNS ANDEXPOSED HELICAL WINDINGS OF ABRASION RESISTANT FILAMENTOUS SYNTHETICMATERIAL WHICH RIDE ON THE COTTON CORES, THE SYNTHETIC MATERIALCONSTITUTING FROM 6% TO 14% OF THE WHOLE FELT BY WEIGHT.